1. Field of Invention
A novel dehydrating agent useful in the processing of histological or cytological samples to dehydrate the same, and in the hydration of tissue samples affixed to a microscopic slide for purposes of hydrating the same before staining and then dehydrating the same after staining.
2. Prior Art
Historically, ethyl alcohol has been used as the liquid dehydrant of choice for treating tissue for histological and cytological examination, both in the processing and staining of tissue specimens. Other liquid dehydrating agents have been proposed. Advantages have been claimed for some of them, but the liquid dehydrant of choice remains ethyl alcohol. Isopropyl alcohol and methyl alcohol alone have not been satisfactory, and neither have more complex liquid dehydrating agents of the same type which have been proposed for the same purpose over the years. A representative U.S. Patent is 2,684,925 (the disclosure of which is incorporated herein by reference) issued July 27, 1954, by Ferrari, which outlines the procedure employed and proposes a new liquid dehydrant comprising as essential ingredients diethylene glycol monoethyl ether acetate and a minor proportion of isopropanol. In acquainting myself with the prior art, the closest patents turned up were 2,150,757, 3,389,052, 3,546,334, 3,961,097, 3,995,022, 4,199,558, 4,221,823, 4,300,243, 4,545,831, and 4,656,047, the search having been conducted in Class 34, Subclass 9; Class 252, Subclasses 194, 364, and 408.1; 424, Subclass 3; and 427, Subclass 2, but these are devoid of any suggestion of the present invention. Although the prior art is replete with suggestions of varying procedure and varying solvents which may be employed for preserving tissue and so on, none of these have really been satisfactory in practice and ethyl alcohol or ethanol continues as the dehydrating solvent of choice despite the fact that it is a controlled substance and therefore subject to nearly unbearable regulation. Suggestions that just any lower alcohol is suitable are totally unfounded in practice, as will be shown hereinafter. Moreover, there simply have been no suitable economic and practical substitutes for ethyl alcohol as a dehydrant in the processing and staining of tissue specimens for histological and cytological examination, up to the time of the present invention. Now, however, it has been possible to provide a suitable substitute for ethyl alcohol which is equally acceptable and in some ways in practice, which provides characteristics which are at least equal to those of ethyl alcohol and in superior thereto when used for the intended purpose as a liquid dehydrating agent, and which moreover is not subject to the burdensome regulation imposed upon controlled substances. It is therefore apparent that a long-felt need of the art here involved has now been fulfilled by provision of the composition and method of the present invention.